Recent trends in the telecommunications industry towards unified communications emphasize the need for converged networks to deliver acceptable quality of service (QoS) for different types of applications with varying QoS needs. Multimedia applications such as Internet telephony are among the end-to-end applications which demand strict QoS guarantees from the underlying data network. Understanding the network behavior at all stages of the deployment of such applications is critical for their performance. For example, at the pre-deployment stage, it is necessary to assess whether the network can deliver the required QoS and more importantly which parts of the network fail to do so. After deployment, monitoring the performance of the network is necessary for maintaining acceptable QoS levels.
Conventional network monitoring and analysis systems are generally not configured to provide an adequate mechanism for understanding link-level QoS behavior in a network. Such information is particularly useful for the purpose of locating the sources of performance problems in a network, but is also useful for many other purposes.
U.S. Patent Application Publication No. 2005/0053009, entitled “Method and Apparatus for Automatic Determination of Performance Problem Locations in a Network,” discloses techniques for automatically determining the particular locations associated with performance problems in a network comprising a plurality of endpoint devices. In one aspect, a network monitoring and analysis system is configured to include a root cause analysis function that permits the automatic determination of performance problem locations in the network. Test communications are generated in accordance with a selected pattern, and end-to-end path measurement data is collected utilizing the generated test communications. The test communications may be directed between pairs of the endpoint devices as specified in the selected pattern. The end-to-end path measurement data is transformed to produce performance indicators for respective non-end-to-end paths defined at least in part by the selected pattern. Such an approach advantageously provides a particularly efficient and accurate mechanism for generating link-level performance indicators in a network, thereby permitting a better understanding of QoS behavior in the network.
Despite the considerable advances provided by the techniques disclosed in the above-cited U.S. patent application, a need remains for further improvements, particularly with regard to the manner in which the endpoint devices used to generate the end-to-end measurements are distributed within the network. Even though the endpoint devices individually are typically not very expensive and not too difficult to deploy, they constitute a limited resource that should be dispensed carefully. Different placement strategies that use the same number of devices may result in varying network coverage. For instance, poor placement strategies may result in situations where no synthetic traffic traverses parts of the network while other parts are excessively probed. Furthermore, link level inference used in the root cause analysis in an illustrative embodiment described in the above-cited U.S. patent application depends on the location of the endpoint devices and the network paths exercised by the traffic injected from the endpoint devices. Poor choice of device locations may undermine the analysis. Hence there is a need for a systematic approach to intelligently place these endpoint devices in the network. Also, it would be desirable to have a technique for accurately estimating the number of endpoint devices that may be required in those implementations in which network topology information is not readily available.